Fluctuation Effects at Pre-Separation Region in Solid ³He-⁴He Mixtures

Abstract

An anomalous temperature dependence of pressure in concentrated solid ³He-⁴He mixtures near the phase separation temperature T _s is first found experimentally. Beginning with temperatures 50–70 mK above T _s , as the temperature decreases and T _s is approached, the pressure increases and continues to increase below T _s in the metastable region. The theory is proposed that gives good quantitative description of the experimental data. The observed temperature dependence of the pressure is completely determined by correlation effects in the impurity subsystem. Due to fluctuations in the local concentration the nuclei of a new phase grow as compact clusters. This effect implies an increase in pressure far from the phase transition onset.